Common AlphaBitmap manipulations in Scol¶

An AlphaBitmap Scol object is a bitmap with an alpha channel. This alpha can be nil.
It can be created from a bitmap object or it can be loaded from a PNG resource file.
All functions of this API are described here.

Create an AlphaBitmap¶

The ObjBitmap8 object¶

This is 8-bits bitmap object insteaf of the 24-bits for the ObjBitmap. Lonely, it is rarely used but it can be an alpha channel.
This API is near than the ObjBitmap API, see Common bitmap manipulations in Scol.

We can create it from a resource file (8-bits BMP file, _LDbitmap8) or from ex-nihilo (_CRbitmap8). Like ObjBitmap, don't forget to destroy them when you no longer needed (_DSbitmap8).

AlphaBitmap¶

The AlphaBitmap type is an opaque Scol type.
Use the Scol function _CRalphaBitmap or _LDalphaBitmap to create a such object.

AlphaBitmap _CRalphaBitmap <channel> <bitmap_object> <bitmap8_object> <background_color> <transparency_color>
The <bitmap_object> is in 24-bits (RVB), <bitmap8_object> is in 8-bits and it is the alpha channel.
See _CRalphaBitmap

@AlphaBitmap _LDalphaBitmap <channel> <reference_reading_png_file>

Destruction¶

When a such object is no longer needed, you should quickly destroy it with _DSalphaBitmap.

How to load a graphic resource file in Scol ?¶

Two near ways enough near if you want to have an ObjBitmap or an AlphaBitmap.
This function is helpful and you should get in your common library.

/* 
Load a graphic resource file
pfile : P : the reading-reference file
channel : channel to loading
return the object to create
fun [P Chn] ObjBitmap
fun [P Chn] AlphaBitmap
*/

fun loadRscFile2ObjBitmap (pFile, channel)=
    if pFile == nil then
        nil
    else
        let _LDbitmap channel pFile -> bmp in
        if bmp == nil then
            let _LDjpeg channel pFile -> jpeg in
            if jpeg == nil then
                let _LDtga channel pFile -> tga in
                if tga == nil then
                    let _GETalphaBitmaps _LDalphaBitmap channel pFile -> [png _] in
                    png
                else
                    tga
            else
            jpeg
        else
            bmp;;

fun loadRscFile2AlphaBitmap (pFile, channel)=
    if pFile == nil then
        nil
    else
        let _LDbitmap channel pFile -> bmp in
        if bmp == nil then
            let _LDjpeg channel pFile -> jpeg in
            if jpeg == nil then
                let _LDtga channel pFile -> tga in
                if tga == nil then
                    _LDalphaBitmap channel pFile
                else
                    _CRalphaBitmap channel tga nil nil nil
            else
                _CRalphaBitmap channel jpeg nil nil nil
        else
            _CRalphaBitmap channel bmp nil nil nil;;